Prophet Muhammad (peace be upon him) fourteen centuries ago ordered kind treatment for the prisoners. They could get their freedom if they paid a small redemption, and some without any thing (some taught Muslim children to read and write as redemption), and no mother was to be separated from her child, nor a husband from his wife.
Prophet Muhammad commanded his companions to be kind to their prisoners, and to put them before themselves when it came to food.God tells us to give food, in spite of our need for it (for the love of Him), to the poor, the orphan, and the captive.
“And they give food in spite of love for it to the needy, the orphan, and the captive,
(saying),We feed you seeking God’s Countenance only. We wish for no reward, nor thanks from you.”(Qur’an 76:8-9)
Islam commands Muslims to show mercy to those combatants who surrender.
“And if any one of the polytheists seeks your protection, then grant him protection so that he may hear the words of God. Then deliver him to his place of safety. That is because they are a people who do not know.” (Qur’an 9: 6)
Prophet Muhammad forbade the killing of women and children. 
The blind, the infirm
and the monks are not to be killed according to Islamic legal scholars as they
are not from among the combatants, similar to the old person.
[Tafsir ibn Kathir: Al-Insan]
 Imam Malik’s Muwatta.